This is a proposal to build and clinically test a transverse section tomographic positron camera for quantative imaging of tumors, gated imaging of the heart, and evaluation of brain and kidney blood flow using positron emitters such as 82Rb, 68Ga and l8F. The system we have designed consists of a circular ring of 280 NaI (Tl) crystals 8 mm x 30 mm x 50 mm. Each crystal is read out by its own photomultiplier to permit high speeds and maximum data control. As verified by tests of crystal pairs, a spatial resolution of 5 mm to 7 mm FWHM (depedng on positron energy) will be possible at data rates in excess of 10,000 per sec. Digital image reconstruction will be performed on a small dedicated computer using algorithms already developed. The device is applicable for either static or dynamic imaging of the brain and other organs as well as gated images of the beating heart. The major application is for the detection of tumors and understanding of cardiac and cerebral vascular disease and physiology.